virtio-vsock is a host/guest communications device. It allows applications in the guest and host to communicate. This can be used to implement hypervisor services and guest agents (like qemu-guest-agent or SPICE vdagent).
- POSIX Sockets API so existing networking applications require minimal modification (unlike virtio-serial char devices)
- Listen sockets can accept connections from multiple clients (unlike virtio-serial char devices)
- No address configuration required inside the guest
- No Ethernet or TCP/IP for a reduced attack surface for hypervisor services
- Can be used with VMs that have no network interfaces
Sockets are created with the AF_VSOCK address family. The SOCK_STREAM socket type is currently implemented for in-order, guaranteed stream semantics.
- Virtio specification: HTML or virtio.git
- Linux kernel: Upstream since Linux 4.8, or see stefanha's linux.git
- QEMU: Upstream since QEMU 2.8, or see stefanha's qemu.git
- Host kernel requirements: CONFIG_VHOST_VSOCK=m
- Guest kernel requirements: CONFIG_VIRTIO_VSOCKETS=m
Launch a guest and assign it CID 3:
(host)# qemu-system-x86_64 -device vhost-vsock-pci,guest-cid=3 ...
- C - use <linux/vm_sockets.h>
- Python - coming in Python 3.7 (already merged upstream)
- Go - Matt Layher's vsock module
Projects using vsock
- nc-vsock - a netcat-like utility for AF_VSOCK
- xpra - X11 persistent remote display server and client
- cloonix_vsock - PTY over AF_VSOCK
- KVM Forum 2015 presentation: virtio-vsock: Zero-configuration host/guest communication (pdf)
- Connectathon 2016 presentation: NFS over virtio-vsock: Host/guest file sharing for virtual machines (pdf)